tracing: instance_rmdir() leaks ftrace_event_file->filter

tracing: instance_rmdir() leaks ftrace_event_file->filter

commit 2448e3493cb3874baa90725c87869455ebf11cd2 upstream.

instance_rmdir() path destroys the event files but forgets to free
file->filter. Change remove_event_file_dir() to free_event_filter().

Link: http://lkml.kernel.org/p/20140711190638.GA19517@redhat.com
Cc: Masami Hiramatsu <masami.hiramatsu.pt@hitachi.com>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Srikar Dronamraju <srikar@linux.vnet.ibm.com>
Cc: Tom Zanussi <tom.zanussi@linux.intel.com>
Cc: "zhangwei(Jovi)" <jovi.zhangwei@huawei.com>
Fixes: f6a84bdc75b5 "tracing: Introduce remove_event_file_dir()"
Signed-off-by: Oleg Nesterov <oleg@redhat.com>
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>